Eh, probably Kubica, in the two years when his car was worth the effort he regularly stole the show, Rosbergs car was faster than Kubicas for much of the season, an I can’t really think of a time when Rosberg was actually preassured for his podium.
Of his three podiums this year China is the only outstanding performance an he lost out because of a mistake while comfortably holding Button, in both Malaysia and Silverstone it was more he did a solid job and everyone else took themselves out of it.
Whereas Kubica has had to really fight tooth and nail, under preassure from cars with far superior performance, Aus, and has pulled it off.
Probably not much in it, but I suspect Kubica would comfortably best him over a season.